Although Leishmania species are estimated to infect about 100 million people worldwide, little is known about the biochemistry of these microorganisms. We have continued to carry out metabolic studies based on the use of metabolic precursors labeled with the stable, NMR sensitive carbon-13 isotope, combined with NMR detection of excreted and extracted metabolites. During the past year, efforts were made to further define the anaerobic metabolism under a variety of conditions. In a N2 atmosphere, glycerol is the major excreted metabolite, with a large pool of glycerol-3- phosphate detectable in cell extracts. In an atmosphere of N2 plus CO2, succinate is the major product, and glucose consumption occurs at a rate comparable to that observed in O2 or O2 + CO2 atmospheres. The consumption of glucose under anaerobic conditions in the presence of CO2 is driven by the formation of malate and NAD+ derived from the reduction of oxalacetate, which in turn is formed from phosphoenolpyruvate plus the CO2. The significance of this pathway is further indicated by studies utilizing 13r- labeled CO2, in which the label is observed at positions 1 and 4 of succinate. Initial observations on the production of D-lactate have been extended to a demonstration of its formation via methylglyoxal synthase and glyoxalases I and II. D-lactate dehydrogenase does not appear to be present. Initial 31P NMR studies of cell extracts have established the presence of a large pool of polyphosphates.